1. Technical Field
The present invention relates to an image processing device, method, and program for extracting a specific region based on the density values of pixels within an input image.
2. Background Art
In the medical field, measuring changes in tumor mass is an important element for clinical evaluation of a cure for cancer, and an objective tumor reducing effect and exacerbation of the original disease have both been used as important endpoints in clinical tests for cancer.
In P. Therasse et al., “New Guidelines to Evaluate the Response to Treatment in Solid Tumors”, Journal of the National Cancer Institute, Vol. 92, No. 3, pp. 205-216, 2000 (Non Patent Literature 1), for example, it is proposed to use the longest diameter of a tumor region and the longest distance in a direction orthogonal to the longest diameter as indices for evaluating the exacerbation of a tumor or the tumor curing effect.
However, this simple measuring of the longest diameter of a tumor region and the longest distance in a direction orthogonal to the longest diameter yields rough measurements of the tumor, not precise area and volume measurements of the tumor.
In another proposal that has been made, a specific region such as a tumor region or a blood vessel region is extracted from a three-dimensional image photographed by a computed tomography (CT) machine or other modalities, and is displayed to be used for medical diagnostic imaging.
A possible way to check the tumor curing effect or the exacerbation of a tumor as described above is, for example, a method in which three-dimensional images of the same patient that are photographed at different points in time are acquired and tumor regions respectively extracted from those three-dimensional images are displayed.
In Japanese Unexamined Patent Publication No. 2009-301254 (Patent Literature 1), for example, there is proposed a method in which three-dimensional images are photographed at different points in time, a first shadow region is detected in one of the three-dimensional images that is photographed at a given point in time, and position information of a given point in the first shadow region is used to extract a second shadow region corresponding to the first shadow region from another of the three-dimensional images that is photographed at another point in time.